Reference is made to copending application Ser. No. 125,099, now U.S. Pat. No. 4,319,328, filed concurrently herewith in the name of Carl A. Eggert entitled "Postage Cost Recording System", said application being assigned to the same assignee as the present invention the disclosure of which is hereby incorporated by reference.
The present invention relates generally to postal weighing, computing and metering devices and more particularly to a driver for positioning the postage amount handles of a postage meter.
Automated mailing systems which may include electric postage scales and postage computers are used to weigh an item and to compute the shipping costs for the item according to such factors as destination and special services or handling which may be desired. Typically, where such systems are used, the shipping amount is manually transferred to a postage meter which prints a postage legend onto the item or which prints the postage legend onto a label that is then affixed to the item. Such postage meters generally include a plurality of postage amount handles that are positioned at specified locations along slightly arcuate paths to thereby adjust the amount which the meter is to print.
It is desirable to accomplish the entire weighing, computing and printing process as quickly and accurately as possible where, for example, large numbers of items must be quickly prepared for shipping. To provide this speed, a meter driver responsive to the postage computer may be employed to automatically position the postage amount handles.
One such postage meter driver is disclosed in U.S. Pat. No. 4,129,815 to Argentine, et al. The meter driver disclosed therein includes stepping motors that drive lead screws which in turn advance or retract drive shoes along guide slots. The drive shoes engage the postage amount handles and position encoders provide signals which indicate the positions of the shoes and thus the handles. This driver, however, employs reversible synchronous stepping motors which are relatively expensive and which require generally complex control circuits. Additionally, lead screws are relatively expensive and difficult to machine and the combination of the stepping motors with the lead screws provide high torque values that can damage the postage meter or the meter driver. Furthermore, the position encoder includes a plurality of conductive wipers that slide along conductive contacts and is therefore subject to undesirable contact bounce, noise and mechanical wear.